A.N. Speca

Chromium(III) and iron(III) perchlorate with the mono-N-oxides of 2,2′-bipyridine and 1,10-phenanthroline

Abstract 2,2′-bipyridine- and 1,10-phenanthroline-mono-N-oxide (bipyNO and phenNO, respectively) chelates with Cr(III) and Fe(III) perchloratws were synthesized and characterized by means of spectral, magnetic and conductance studies. The new complexes are of the types [M(bipyNO)3](CIO4)3 2H2O and [M(phenNO03] (CIO4)3 (M = Cr, Fe). the mono-N-oxides act as bidentate O,N-chelating agents. The bipyNO complexes contain lattice water. The UV bands of bipyNO exhibit larger shifts and splittings tahn those of phenNO, upon metal complex formation. BipyNO exisrs in the trans-form in the crystal and assumes a configuration close to the cis-form in its metal chelates, whereas free phenNO is rigidly held in the cis-form in the crystal, and has the same conformation in its chelates. The electronic spectra of the complexes are characterized by stron metal-to-ligand charge-transfer bands. Approximate Dq parameter calculations for the Cr(III) complexes indicate that bioyNO and phenNO are weaker ligands than the parent bases and stronger ligands than the corresponding N,N-dioxides. The Cr(III) complexes are magnetically normal, but the Fe(III) compounds ehibit temperature-dependent magnetic moments (3.02-3.67 BM for the bioyNO acid, 1.98-2.52 BM for the phenNO complex, over the temperature range 80-313°K), wgich were attributed to the existence of spin-free-spin-paired equilibria.

Nicotinic and isonicotinic acid n-oxide interactions with 3d metal perchlorates[1]

Interactions of nicotinic or isonicotinic acid N-oxides (N-nicOH and N-inicOH, respectively) with 3d metal (II) perchlorates in ethanol-triethyl orthoformate lead, in most cases, to partial substitution of perchlorate with nicotinate (N-nicO) or isonicotinate(N-inicO) N-oxide anionic groups. These reactions led to the isolation of the following new metal complexes: Ni(N-inicOH)3(ClO4)2·3H2O: the only true adduct of the series, apparently polynuclear, with both unidentate terminal and bidentate bridging N-inicOH, bridging O2ClO2 ligands, ionic ClO4− and lattice water. Complexes with exclusively anionic ligands of the type (ClO4) (MMn, Cu for LN-nicO; MCu for LN-inicO), with both terminal and bridging L, ionic and unidentate coordinated perchlorate, and aqua ligands. The rest of the complexes are of the mixed ligand type, i.e.: [H2O)2(O3ClO)M(N-nic)2M(N-nicOH)(OH2)2] (ClO4) (MCo, Ni), with bridging N-nicO, terminal N-nicOH,-OClO3 and aqua ligands, and ionic ClO4−; M4(N-inicOH) (N-inicO)5 (ClO4)3. 4H2O (MMn, Co, Zn), polynuclear with exclusively bridging organic ligands, terminal aqua and bidentate perchlorato groups, and ionic ClO4−; and, Zn4(N-nicOH)N-nicO)5(ClO4)3. 10H2O, probably tetrameric, with four bridging and one terminal N-nicO groups, and terminal N-nicOH, aqua and =O2ClO2 ligands, as well as ionic ClO4−. With the exception of the latter complex, which is hexacoordinated, the new metal complexes appear to be pentacoordinated. The likely structural types proposed for these compounds were based on the overall spectral and magnetic evidence obtained.

Characterization studies of adenine complexes with 3d metal perchlorates

A series of adenine (LH) complexes with 3d metal perchlorates were prepared by refluxing solutions of the metal salts in ethanol-triethyl orthoformate with the ligand for 2–5 days. Our studies indicate that, depending on the ligand to metal molar ratio employed and the duration of the refluxing step, complexes with either neutral LH or anionic L− can be obtained. Among the new complexes, Cu(LH)2(ClO4)2·C2H5OH appears to be of the familiar dimeric type with quadruple bridges of N(3), N(9)-bonded LH, one terminal -OClO3 ligand per Cu2+ ion and lattice ethanol (μeff = 1.66 μB at 298K.). The Fe3+ complex (μeff = 2.39 μB) seems to be also a dimer of the [(O2ClO2)(LH)2FeL2Fe(LH)2(O2ClO2)] type, with N(9)-bonded terminal and N(y), N(9)-bonded (y = 1, 3 or 7) bridging adenine. A similar type of bridging (N(y), N(9)-bonded) adenine is also present in the probably double-bridged dimeric FeL(ClO4)·C2H5OH·2H2O complex (μeff = 4.86 μB), and a number of presumably linear, single-bridged polymers of the M(LH)2(ClO4)2·χC2H5OH (x=2 for M = Mn; x=3 for M = Co) and ZnL(ClO4)·C2H5OH·3H2O types. However, the two remaining complexes of the ML(ClO4)·C2H5OH·2H2O (M = Co, Ni) type, involve adenine apparently coordinated through the NH2 nitrogen. For these compounds, linear polymeric single-bridged structures with N(6), N(z)-bonded (z is most probably 9) bridging L, were considered as likely. The ambient temperature magnetic moments of the complexes considered as linear polymers range from slightly below normal to normal, but it is anticipated that studies at 300-80K. will reveal magnetic exchange interactions in general, in view of the established spin-spin coupling in the corresponding purine complexes.

Purine complexes with divalent 3d metal chlorides

Abstract A series of purine (puH) complexes with 3d metal(II) chlorides were prepared by interaction of ligand and metal salt in ethanoltriethyl orthoformate. 1:1 complexes of the general type M(puH)Cl 2 ·nH 2 O (n = O for M = Zn; n = 1 for M = Fe, Co, Cu; n = 2 for M = Mn, Ni) were isolated. Spectral evidence favors a tetrahedral configuration for Zn(puH)Cl 2 , and coordination numbers five for M(puH)Cl 2 ·H 2 O (M = Fe, Co, Cu) and six for M(puH)Cl 2 ·2H 2 O (M = Mn, Ni). The new paramagnetic metal ion complexes are characterized by normal ambient temperature magnetic moments for high-spin 3d 5 –3d 8 compounds or the 3d 9 configuration. A linear oligomeric structural type, involving single-bridged MpuHMpuHsequences and exclusively terminal chloro, and wherever applicable, aqua ligands was considered as most likely for the new complexes. Probable bonding sites of the bidentate bridging puH ligands are the N(3) and N(9) nitrogens.

Transition metal perchlorate complexes with pyrazine N-oxide

Complexes of the mono N-oxide of pyrazine (pyzNO) with 3d metal perchlorates were synthesized by allowing ligand and hydrated metal salt to interact in ethanoltriethyl orthoformate. The new complexes were characterized by means of spectral and magnetic studies. Possible structures discussed are as follows: [Cu(NC4H4NO)4(OH2)(OClO3)](ClO4), monomeric and hexacoordinated with N-bonding pyzNO ligands. [Zn(ONC4H4N)n(NC4H4NO)4−n(OH2)(OClO3)](ClO4) (n = integer < 4), also monomeric and hexacoordinated, but with both N- and O-bonding unidentate pyzNO ligands. Hexacoordinated complexes, apparently binuclear, involving both uni-(O-bonding) and bi-(O,N-bonding, bridging) dentate pyzNO groups: [(NC4H4NO)3(C2H5OH)Cr(NC4H4NO)2-Cr(C2H5OH)(ONC4H4N) 3](ClO4)6; [(NC4H4NO)2(H2O)(O3ClO)M(NC4H4NO)2M (OClO3)(OH2)-(ONC4H4N2](ClO4)2 (m = Fe, Co); and [(NC4H4NO)2(H2O)2Ni(NC4H4NO)2Ni(OH2)2(ONC4H4N)2]-(ClO4)4. Mn(pyzNO)4(ClO4)2 and Fe(pyzNO)3(ClO4)2 are probably bi- or poly-nuclear and of the following types: [(NC4H4NO)nM(NC4H4NO)2M(ONC4H4N)n](ClO4)4 (n = 3 for Mn; n = 2 for Fe) or [M(pyzNO)3,4]χ(ClO42χ, involving polynuclear complex cations with one (Fe) or two (Mn) terminal O-bonded pyzNO and two bridging, bidentate O,N-bonded pyzNO ligands per metal ion. Fe(III) perchlorate yields a 1:6 complex with pyzNO; no characterization of the bonding site of the ligand was possible from the available experimental evidence, but the above metal-to-ligand ratio is suggestive of the presence of O-bonded, unidentate ligands ([Fe(ONC4H4N)6](ClO4)3).

Isonicotinate n-oxide complexes with dipositive 3d metal ions [1]

Abstract Divalent 3d metal complexes with isonicotinate N-oxide (N-inicO), of the type M(N-inicO)2·xH2O (M = Mn·Zn; x = 6 for M = Fe, Co, Ni, Zn; x = 5 for M = Mn; x = 2 for M = Cu), were prepared by reaction of (N-inicO)NH4 with the corresponding metal(II) acetates or ferrous ammonium sulfate in water. Desiccation of the preceding complexes over P4O10, under a vacuum of 10−4 torr, led to partial dehydration, affording the following lower hydrates: x = 5for M =Ni; x = 1.5 for M = Co, Zn;x = 1 for M = Cu; x = 0.5 for M = Mn, Fe. Characterization of the new metal complexes, based on spectral and magnetic studies, and the insolubility of all the complexes in water and organic solvents, led to their formulation as polynuclear of the following types: Hexa- and penta-hydrates; hexa-coordinated, [M(N-inicO)2(OH2]n·mH2O (m = 4n for M = Fe, Co,Ni, Zn; m = 3n for M = Mn, Ni), with the N- incO ligands forming single bridges between adjacent metal ions and functioning as bidentate, coordinating through the NO and one of the carboxylate oxygens; part of the non-coordinated COO oxygens are hydrogen-bonded to water, which is present in the form of both aqua ligands and lattice H2O. The lower hydrates of the type [(N-inicO2M-(OH2)-M(N-inicO)2)]n· bridging acqua ligand per two metal ions, as well as bidentate bridging N-inicO, being pentacoordinated of the type [(N-inocO)2M-(OH2)-M(N-inico)2]n· mH2O (m = O for M = Mn, Fe; m = 2n for M= CO, Zn). The dihydrate Cu(II) complex appears to be square-planar of the type [Cu(N-inicO)2]n·2nH2O, with bidentate bridging N-inicO ligands and exclusively lattice and H-bonded water. The corresponding monohydrate ([Cu(N-inicO)2]n·nH2O) probably contains both tetra-and penta-coordinated Cu2+ ions, with some N-inicO ligands acting at bidentate and some as tridentate (coordinating through the NO and the two COO oxygens) bridging. N-inicO is a 1igand of about the same strength as picolinate- and nicotinate-N-oxides.

2,2′-bipyridine n-oxide and 1,10-phenanthroline n-oxide complexes with divalent 3d metal nitrates☆

Abstract The synthesis of divalent 3d metal nitrate complexes with 2,2′-bipyridine N-oxide (N-bipyO) and 1,10-phenanthroline N-oxide (N-phenO) is reported. The new complexes were characterized by means of their i.r. and electronic spectra, magnetic moments, and molar conductivities in solution. In the case of N-bipyO, mixed ligand complexes, i.e. containing both ligand and nitrate coordinated to the central metal ion, are formed. For N-phenO both tris and mixed ligand complexes are formed and in some cases may be obtained from the same metal ion. The nitrate anion exhibits bidentate, monodentate, and ionic modes of bonding in the mixed ligand complexes. The mono N-oxides function as bidentate, O,N-chelating agents. The u.v.-spectra of the new metal complexes are characterized by the presence of ligand, electron-transfer (metal-to-ligand) and (d-d) bands.

1,10‐PHENANTHROLINE N‐OXIDE CHELATES WITH 3D METAL PERCHLORATES

Abstract The synthesis of divalent 3 d metal perchlorate chelates with 1,10-phenanthroline mono-N-oxide (phenNO) is reported. The new complexes were characterized by means of their i.r. and electronic spectra, magnetic moments molar conductivities in solution and X-ray powder diffraction patterns, and formulated as [ M (phenNO) 3 ](ClO 4 ) 2 ( M  Mn, Fe, Co, Zn) [Ni(phenNO) 3 ] ClO 4 ) 2 . 2H 2 O, and [Cu(phenNO) 2 ](ClO 4 ) 2 . PhenNO acts as a bidentate O,N-chelating agent. The Ni(II) complex contains lattice water. The u.v.-visible spectra of the new metal chelates are characterized by the presence of ligand, charge-transfer (metal-to-ligand) and ( d − d ) bands. The spectrochemical parameters for the phenNO complexes suggest that this compound is a considerably weaker ligand than 1,10-phenanthroline. This is also demonstrated by the fact that the latter ligand forms a spin-paired [FeL 3 ] 2+ complexes, whereas the corresponding phenNO complex is spin-free.

Transition metal acetate reactions with nicotinic and isonicotinic acid N-oxides

Abstract Reactions of M(II) acetates (M = Mn, Co, Ni, Cu, Zn) with nicotinic or isonicotinic acid N-oxides (N-nicOH and N-inicOH, respectively), in ethanol-triethyl orthoformate solution, lead to partial substitution of acetate with nicotinate (N-nicO) or isonicotinate (N-inicO) N-oxide anionic groups. Complexes of the following types were precipitated during these reactions: Mn 2 (N-nicO)(CH 2 COO) 3 ·6H 2 O; M(N-nicOH)(N-nicO)(CH 3 COO)·xH 2 O (x = 0 for M = Co, Zn; x = 2 for M = Ni); Cu 2 (N-nicOH)(N-nicO) 2 (CH 3 COO) 2 ; and M 2 (N-inicOH)(N-inicO) 2 (CH 3 COO) 2 ·xH 2 O (x = 1 for M = Mn, Zn; x = 2 for M = Cu; x = 4 for M = Co, Ni). Bi- or poly-nuclear structures were proposed for these complexes, on the basis of characterization studies. The N-nicO and N-inicO ligands appear to be invariably bridging, and the acetato groups terminal (bidentate chelating in most cases). The neutral N-nicOH and N-inicOH ligands were found to act in certain cases as terminal, unidentate, NO oxygen-bonded, and in other cases as bridging, bidentate, coordinating through the N-O and CO oxygens. The Mn(II), Co(II) and Ni(II) complexes are normal high-spin compounds of these metal ions. Cu 2 (N-inicOH)(N-inicO) 2 (CH 3 COO) 2 ·2H 2 O also exhibits normal magnetic behaviour at 305-80°K. However, its analogue with the N-nicOH and N-nicO ligands shows a μ eff decrease of 0.2 μB over the same temperature range, owing to antiferromagnetic exchange between adjacent Cu 2+ ions, in a highly cross-linked polynuclear structure.

Adennine N(1)-oxide complexes with first row transition metal perchlorates

Abstract A series fo adenine N(1)-oxide (LH) complexes with 3d metal perchlorates were prepared by refluxing mixtures of ligand and salt in ethanol-triethyl orthoformate. Charaterization studies revealed significant differences in ligand binding sites and probable complex structural types, with metal ion variation. Thus, [Cr(LH)2(OClO3)2(EtOH)2(ClO4) and [M(LH)2(OClO3)(EtOH)2](ClO4) (M = Mn, Zn) seem to be monomeric with unidentate, imidazole nitrogen-bonded (most porbably N(7) LH, while the Co2+ analogue of the latter two complexes is apparently a linear polymer, with single bridges of bidentate O(1), N(7)-bonded LH, as well as terminal unidentate imidazole introgen-bonded ligand groups. The rest of the complexes involve both neutral LH and anionic L− ligands. The subnormal room temperature magnetic moment of the Cu2+ complex (1.68 μB) favours a triple ligand-briged structure of the [(O3ClO)Cu(LH)L2Cu(OClO3)] type, with O(1), N(7)-bonded bridging ligands. Ni(LH)L(ClO4)·2EtOH and Fe(LH)2L(ClO4)2 were considered as linear polymers, with single bridges of O(1) N(7)-bonded adenine N(1)-oxide ligands; the rest of the ligands present seem to be terminal, unidentate imidazole nitroten-bonded for M = Ni2+ and bidentate chelating, O(1), N(6)-bonded for M = Fe3+.